Workload allocation for one or more tools in a laser cloth cutting system

ABSTRACT

A cloth cutting system wherein cloth is carried in a single layer into a cutting area wherein a laser beam is focused on the cloth and is directed by computer commands to travel within the cutting area so as to cut a plurality of patterns through the cloth rapidly and accurately.

.afi m United States Patent Hasslinger 1 Oct. 30, 1973 [54] WORKLOAD ALLOCATION FOR ONE OR 3,626,141 12/1971 Daly 219/121 L MORE OO IN A LASER CLOTH 3,614,369 10/1971 Medley 219/121 LM CUTTING SYSTEM [75] Inventor: Robert L. Hasslinger, Simi, Calif. Primary Examiner C' L Albrmon [73] Assignee: Hughes Aircrait Company, Culver Assistant Momanye Cit C lif, Attorney-W. H. MacAllister, Jr. et al.

[22] Filed: Jan. 19, 1972 [21] Appl. No.: 218,958

57 ABSTRACT [52] US. Cl.. 219/121 LM, 83/925 CC, 235/l51vl1 [51] Int. Cl 1323b 27/00 A cloth ing y m wh r i cloth is carried in a [58] Field of Search 219/ 121 L, 121 EB; ng layer in a cutting area wherein a laser beam is 444/1; 340/1725; 233/1 51 11; 83/71, 925 focused on the cloth and is directed by computer com- CC, 203, 216, 217 mands to travel within the cutting area so as to cut a plurality of patterns through the cloth rapidly and ac- [56] References Cited curately.

UNITED STATES PATENTS 3,636,525 l/1972 lnaba et a1 340/1725 14 Claims, 15 Drawing Figures Control Ponel 2 3! 33 l9 1 25 23 i Laser Moieriol Positioning Power Handling 0 Dlgliol l Electronics Supply Electronics Deck Computer I 1: i F Lo s e r l l I l L i i l l c l 9 g o L- Y i l a) l 2 8 3 0 i i C 5 I E (n L j I 8 I 1 J 5 Material I Handling Electronics Loser Power pp y Fig.1.

SHEET 01 0F 10 Positioning Dlgltol I Electronics Computer Control Panel PATENTEDUU 30 mm ,7 [5 Cuttin Area PATENIEUnmsonars 3.769%88 saw near 10 Pmmmmaoma 3,769,488

sm user 10 FATENTED DU 30 I975 Sim u? or 10 :mn 307m Eoamkrw fromiig. 13.

PAIENIEDnm 30 1915 3769,1188

saw 090? 10 XDDA 277 I 237 279 x AXIS K R REGISTER Z c :COMMANDS cos 6 FROM 4 COMPUTER cos a 265Y AX x DIRECTION FROM (TO COMMAND coMPuTE I22 counnza- 269 INPUT common DOWN COUNT AX COUNTER ZERO ZERO REGiSTER DETECTOR DETECTOR CLEAR (ALL REGISTERS) DWELL ENABLE FEEDRATE GENERATOR BLOCK LOAD 30 km 30 m1 MAX DWELL DOWN TO COMPUTER RAH COUNTER 283 285 273 ZERO DWLLL DETECTOR TIMZ FROM 100 COMPUTER I22 oow- A v Av COUNTER coum FROM COMPUTER I22 T aw DIRECTION (TO COMMAND 265x COUNTER- INPUT cormzou sm 9 sm 5 mom COMPUTER I c v R REGISTER 2 E v COMMANDS Y to Fig 15 1 J Y DDA 277 Crossarm Controllers SHEET 10 0F 10 cLocK REFERENCE REsDLvER I OSCILLATOR -COUNTER SUPPLY TO ALL TO ALL CROSS AR I COMMAND 293 "g; POSITION FEEDBA INPUT c0UNTERs RESOLVERS COURT; I ,309 I I 3"... J

CUMMAND EXTENDED X AXIS COUNTER coMMAND I RANGE sERvo AMP X AXIS I coNTRoL COUNTER I PHASE I AND MDTDR MOTOR I Lem DISCRIMINATOR I CONTROL I I I I 3|3 L 297 I39 x AXIS 2 5 I I POSITION 3|8 coMMANDs I I +v -v I 3| 5 3|4 CONVEYOR PosmoN I 3 9 3l6 SENSE PINS SENSOR sENsoR REsET AMPLIFIER I INTEGRATOR 'ggIIS AND MOTOR CONTROL I MOTION INPUT coNTRoL I cDNTRoL CLOCK ENABLE I I COMMAND EXTENDED XAXIS COUNTER COMMAND RANGE SERVO AMP CONTROL couNTER PHASE AND MOTOR I LOGIC DISCRIMINATOR CONTROL I I A WIS 309 307 3H3 I POSITION FT ANGLE COMMANDS x AXIS coNTRoL, 0 PHASE I TYPICAL, 3 PLACES ANGLE CONVERTER 29 I 293 I .NPUT REF. VOLTAGE coNTRoL cLocK I I I T 297 coMMAND I EXTENDED YAXIS' I coUNTER COMMAND RANGE sERvo AMP Y AXIS CONTROL COUNTER PHASE AND MOTOR MOTOR I LOGIC I DISCRIMINATOR cDNTRoL I A I I; 309 307 I313 an I sTTTDN I SHAFT ANGLE LL MMANIB vg CO-TRDL TO PHASE I R I\ HEAL J IL-MES ANGLE 9- 2 3 cDNvERTER REF. VOLTAGE WORKLOAD ALLOCATION FOR ONE OR MORE TOOLS IN A LASER CLOTH CUTTING SYSTEM CROSS REFERENCES TO RELATED APPLICATIONS MATERIAL CUTTING AND PRINTING SYSTEM filed concurrently herewith by William J. Mason, Douglas W. Wilson, Douglas M. Considine, Felix Jerome Viosca and J. Philip Wade.

Howard R. Friedrich, application Ser. No. 3,627 for a LASER LENS COOLING SYSTEM filed Jan. 19, 1970 now US. Pat. No. 3,696,230, discloses a system wherein a stream of gas is used to cool a laserbeam focusing lens and also for controlling combustion of the material being cut.

An improved working surface featuring knife-edged supports is the subject of application Ser. No. 218,896 filed by Georgette S. Egan on a WORKING SURFACE FOR RADIANT ENERGY BEAM CUTTER concurrently herewith.

A system whereby a laser beam is movable on a selected surface without moving the beamss source is the subject of application Ser. No. 187,712 filed by Robert M. Zoot and Douglas W. Wilson on a LASER CUT- TER OPTICAL SYSTEM concurrently herewith.

MATERIAL HOLDING AND SMOKE REMOVAL SYSTEM FOR A LASER CUTTER, application Ser.

No. 184,139, filed on Sept. 27, 1971 by Rodolfo Castro and Esteban J. Toscano, discloses a system for both holding in place fabric being cut and for removal of combustion by-pro ducts from the cutting area both above and below the cloth.

CONVEYOR ADVANCING SYSTEM, application Ser. No. 218,933, filed concurrently herewith, by Robert L. Hasslinger, William 1. Newton, Esteban J. Toscano and Rodolfo Castro discloses a system for compensating positioning errors in a conveyor upon which material to be cut may be carried.

A system for controlling combustion of material being cut by a laser beam and for keeping debris out of a laser focusing system is the subject of application Ser. No. 202,422 filed on ENVIRONMENTAL CONTROL AT LASER CUTTING POINT'by Rodolfo Castro, William J. Newton TENSION FREE CLOTH DISPENSING APPARA- TUS, application Ser. No. 157,247 filed on June 28, 1971 by Rodolfo Castro, William J. Newton and Esteban J. Toscano discloses a system for dispensing fabric from a roll onto a conveyor without stretching the fabric. The above reference applications are assigned to the same assignee of this application.

BACKGROUND OF THE INVENTION The present invenion relates to a system and a method for guiding one or more tools, such as cutters, along a layer of material according to preselected, stored patterns. More specifically, the invention relates to the allocation of such patterns to a tool so that as successive portions of the material are positioned within the work area of the tool, it will receive those, and only those signals which define the patterns that correspond to the material so positioned.

In the above-referenced Considine et a1. application for MATERIAL CUTTING AND PRINTING SYS- TEM there is disclosed a system designed to cut parts for garments from cloth carried in a single layer.

and Esteban J. Toscano on Nov. 26,

As described by Considine et al., material to be cut is laid upon a work support surface which is then moved, together with the material lying thereon, into a cutting area. Within the cutting area a plurality of spaced apart pieces are cut to preselected patterns from the material by moving a cutting tool, in the form of a focused radiant energy beam, in accordance with numerical commands. Once the cutting is completed, the work support surface with the cut pieces thereon is moved out of the cutting area. In developing the fabric cutter, it has become apparent that its productivity could be greatly increased by positioning more than one cutting tool along an elongate work support surface such as that of a conveyor so that they could all be cutting parts substantially concurrently.

OBJECTS OF THE INVENTION The primary object of the present invention is to provide a method for allocating to each of several tools its proper share of patterns to be cut and to do it simply, with a minimum of decision-making being required as to which tool is to cut which pattern.

A related object of the present invention is to provide a system wherein material is passed through the work areas of two or more tools operating on the material in response to stored signals representing patterns to be followed by the tools, and wherein each pattern is assigned to a particular tool so that as the portion of the material which is to receive a particular group of patterns is positioned completely within the work area of a given tool, that too] will operate upon the material in response to the signals representing that group of patterns.

BRIEF DESCRIPTION OF THE INVENTION In accordance with that aspect of the present invention whereby a plurality of tools are guided along the perimeters of a set of patterns distributed along an elongate surface movable along its longitudinal axis in response to recorded signals representing the perimeters and locations of those set of patterns in their desired positions on that surface, there is assigned to each tool an area of operation which extends along the longitudinal axis of the elongate surface by a length which is at least twice the longest dimension of any of the patterns along that axis, and the areas of operation are spaced apart along that axis.

In operating the system in accordance with the present invention, the elongate surface is advanced along its longitudinal axis through the aforesaid areas of operation in equal steps so that after each step a successive one of a first series of spaced apart pattern groups is positioned fully in one of the areas of operation. Moreover, the areas of operation are spaced from one another so that after each step a successive one of a respective additional series of spaced apart pattern groups, whose member groups alternate cyclically with member groups of the first series of spaced apart pattern groups, is positioned fully in each of the other areas of tool operation. After each step, each tool is actuated with the signals representing the patterns in the pattern group then located in the area of operation of that tool. In this manner each tool is operative to cut its assigned group of patterns concurrently with all of the other tools.

For sake of a concrete example let it be assumed that three tools extend along the elongate surface and that the set of patterns along which those tools are to be guided are divided into nine groups, each group occupying a successive portion of the elongate surface along its length. Then, in accordance with the invention, the first series of spaced apart groups will include the first, fourth and seventh group of patterns, the second series will include the second, fifth and eighth group of patterns and the third series will include the third, sixth and ninth group of patterns. After the first step there will be positioned in the areas of operation of the three tools the first, fourth and seventh group of patterns. After the second step the second, fifth and eighth group of patterns will be so positioned, and after the third step it will be the third, sixth and ninth group of patterns which are positioned within the areas of operation of the three tools.

In further keeping with the present invention each pattern is allocated to the proper tool by assigning to each tool a respective series of spaced apart, transverse, equally wide segments of the elongate surface, with members of the respective series cyclically alternating. For example, with three tools and nine successive pattern groups, the elongate surface is divided into nine successive transverse segments of equal width and they are assigned to the respective tools in the following three series. Tool 1: segments 1, 4 and 7. Tool 2: segments 2, and 8. Tool 3: segments 3, 6 and 9. Thus the members of the respective (T1, T2, T3) series of transverse segments (1, 4, 7; 2, 5, 8; 3, 6, 9) alternate cyclically: T1, T2, T3, T1, T2, T3, T1, T2, T3. Moreover, the tools are so spaced along the longitudinal axis that after each advancement of the elongate surface along that axis a successive segment of a respective series of segments is centered in each of the tool areas of operation. Thus, after the first advancement the first of each of the three series of segments will be centered, after the following advancement the second of each series will be centered and after the third advancement the last of each series will be so centered. Finally, after each advancement there are applied to each tool the signals representing those patterns whose longitudinal midpoints along the longitudinal axis fall within the segment that is centered in the area of operation of that tool.

Since each segment is no wider than half the length of the area of operation to which that segment is allocated, and since the tool in that area of operation receives the signals for only those patterns whose longitudinal midpoints fall within that segment, the tool will be capable of following each of those patterns fully along their perimeters, it following from the above-defined geometry that each of those patterns will fall fully within the tools area of operation.

BRIEF DESCRIPTION OF THE DRAWINGS Additional objects and advantages of the invention will become apparent from the following detailed description with reference to the drawings in which:

FIG. 1 is a block diagram of an exemplary system in which patterns are cut out of cloth by means of a focused laser beam;

FIG. 2 is an exemplary focusing device using refractive optics which serves to redirect a laser beam from a direction parallel to the material to be cut into a second direction at the material and also to focus the beam;

FIG. 3 is an alternative focusing device for accomplishing the same purpose but using reflective optics;

FIG. 4 illustrates the manner in which the smoke generated by the cutting laser beam is removed from above and from below the material which is being cut;

FIG. 5 is a perspective view of the exemplary system including a long conveyor made up of relatively thin honeycomb slat assemblies, and also showing the carriages for traversing laser beams and printing devices over material lying thereon;

FIG. 6 is a perspective view, partially broken away, of a suitable slat assembly for the conveyor of FIG. 5;

FIG. 7 is a perspective view of a crossarm assembly, of which four are shown in FIG. 5, and which is adapted to traverse a cutting tool or a printing device and in particular the focusing device of FIG. 2 or FIG. 3 over a predetermined work area above the conveyor assemy;

FIG. 8 illustrates a typical pattern cut by means of the system of FIG. 5;

FIG. 9 illustrates an acceptable path approximation in traversing corners;

FIG. 10 illustrates the location in accordance with the present invention of the work areas in which cutting takes place along the conveyor and the manner in which the workload is distributed in accordance with the present invention between the several cutters;

FIG. 11 illustrates a portion of a marker which includes several patterns laid out so as to waste a minimum of material and cut by means of the apparatus illustrated in FIG. 5 in accordance with the present invention;

FIG. 12 is a flow chart which illustrates how the stored digital signals are created for producing a desired marker and how those signals are used to control various parts of the system;

FIG. 13 is a block diagram showing the organization of a computer suitable for driving numerical controls associated with the respective crossarms;

FIG. 14 is a block diagram ofa numerical control for driving the servomechanisms of one of the crossarms in response to signals received from the computer of FIG. 12;

FIG. 15 is a block diagram of a suitable crossarm servomechanism.

GENERAL DESCRIPTION OF AN EXEMPLARY EMBODIMENT OF THE INVENTION An exemplary radiant energy cutting system illustrating the principles of the present invention is shown generally in FIG. 1. The system as disclosed herein with reference to FIGS. 1-9 and 13-15 is the invention of Mason et al by whom the referenced MATERIAL CUTTING AND PRINTING SYSTEM is being filed. That system is disclosed herein primarily as background. The present invention may be directly gleaned from Section 3 with reference to FIGS. 10, 11 and 12. In the exemplary system disclosed herein, and illustrated generally in FIG. 1, the cutting tool is a beam of coherent light generated by a laser beam source 11 which is preferably stationar and is aimed at a cutting plane within a cutting area 13 by means ofa pair of optical devices 14 and 15. In a manner to be described shortly hereinafter, by appropriately moving the optical device 14 and 15 the laser beam produced by the source 11 can be traversed over the cutting area 13 so as to excute any desired route. It will be sufficient to note at this point that the laser beam' remains unfocused during the initial portions 11a and 11b of its travel and is focused only in the second optical device so as to become focused in the cutting plane which lies in the cutting area 13.

Material which is to be cut by the focused beam in the cutting area 13 is supported in a single flat layer upon a supporting structure 17 which preferably takes the form of a conveyor. It should be noted that, while the system disclosed herein finds its greatest utility and advantage in permitting material to be cut at an economical rate in a single layer, the system could also be usefully employed where more than one layer is to be cut limited only by the optical depth of focus. However, for purposes of the description which follows, operation of the system will always be described with reference to the cutting of a single layer of material. In the exemplary system, the material from which parts are to be cut is a fabric which is unrolled from a bolt in a single continuous layer onto the conveyor 17 which is advanced in a series of equal steps so as to carry successive portions of the fabric lying thereon into the cutting area 13. After each advancement of the conveyor 17, parts are cut to patterns from the material lying within the cutting area 13, with each discrete cutting operation preformed being referred to as a bite.

To traverse the focused laser beam in the cutting area 13 so as to cutout a plurality of separate parts, the optical devices 14 and 15 are moved together in the X direction (parallel to the longitudinal axis of the conveyor l7) and the optical device 15 is moved relative to the optical device 14 in the Y direction which is at right angles to the Y direction. These movements are effected by positioning devices which are moved under the control of a positioning electronic circuit 19 whose principal function is to produce, in response to numerical commands generated by a digital computer 21, electrical signals compatible with the devices used to move the optical devices 14 and 15. The commands produced by the computer 21 are in turn derived by means of a tape deck 23 from a cutting sequence tape 25 upon which are stored signals which represent the locations and perimeters of the parts which are to be cut from the material in the cutting area 13. Preferably after each part has been cut, the laser beam is interrupt ed electronically and the beam traversing apparatus which carries the optical devices 14 and 15 is moved to the starting point of the next part at which time the laser beam is re-established.

While interruption of the laser beam could be accomplished by means of a mechanical shutter interposed in the unfocused portion of the beams path, in FIG. 1 a laser power supply 27 is shown to be responsive to the digital computer 21 and to a control panel 29 through lines 31 and 33 respectively. The function of the control panel 29 is to turn on the subsystems such as the computer 21, the positioning electronics 19, the laser power supply 27 and to coordinate them with one another. Thus, for example if, by conventional means such as limit switches or voltage sensors, it is detected that the device for positioning the optical elements 14 and 15 is inoperative, an interlock in the control panel 29 prevents the laser 11 from turning on. Similarly, the control panel 29 will prevent automatic operation of the overall system unless all of the sybsystems are operational. Additionally, manual commands may be made by means of conventional pushbuttons provided on the control panel and various indicating lights on the panel apprise the operator of the condition at various points in the system.

Advancement of the conveyor 17 is by means of a conveyor drive 35 such as an electric motor coupled through gears and drive'sprockets to a pair of chains by means of which the conveyor 17 is advanced. Operation of the conveyor drive 35 is controlled by a material handling electronics subsystem 37 which is responsive to commands received from the digital computer 21 over a line 39 and which is also connected to the control panel 29 through a line 41 for the previously stated purpose. Switching of the laser power supply 27 and starting and stopping of the conveyor drive 35 through the material-handling electronics 37 may be accomplished either in response to command signals recorded on the production tape 25 or in response to command signals which are derived by means of the digital computer 21 from the information which it receives from the tape 25. Thus, the computer 21 may automatically produce the control signals necessary to operate the laser power supply 27 and the material-handling electronics 37 so that the laser power supply is turned on and off as each part is started and finished, while the material-handling electronics are started and stopped as each'complete bite is begun and completed. Also controlled by the material-handling electronics 37 is a material spreader 43 whose function is to dispense the fabric from a bolt in step with the advancement of the conveyor 17 so that the material is deposited on the surface of the conveyor without stretching or wrinkling it excessively.

Summarizing this brief description of the exemplary system, the patterns to which parts are to be cut from the fabric being advanced by the conveyor 17 are recorded on the cutting sequence tape 25 so that as successive portions of the material are positioned within the cutting area 13, the digital data representing the patterns to which parts are to be cut from those portions are made available to the digital computer 21. The digital computer 21 processes the data associated with the particular portion of material in the cutting area 13' and applies that data in slightly different form, and with additional information generated by the computer, to the positioning electronics 19. The latter, in response, applies control signals to the devices which move the optical devices 14 and 15 so as to traverse the laser beam according to the electronically stored taped patterns.

Before each part is cut, it is preferable that the laser beam positioning optical elements 14 and 15 be moved so that when the laser beam is turned on it will be at the starting point of that part. Then the devices 14 and 15 are moved so as to rapidly traverse the laser beam around the perimeter of the part and when the beam has reached the end point of the part, which will typically intersect its starting point, the beam is turned off and the optical devices 14 and 15 are moved to the starting point of the next part to be cut. When all of the parts which are to be cut during a given bite have been completed, the conveyor 17 is advanced so as to bring the next portion of the material into the cutting area 13, the system also being operative at this time to dispense material from the spreader 43 onto the conveyor.

As will be shown in more detailed drawings of the system, it may also include means for marking any of the parts which have been cut out of the material with information that can be used when those parts are sewn together into a garment. Thus, sewing lines for the garment into which the parts are to be made can be written onto these parts by a non-contact printing device which is translated in a manner similar to the manner in which the laser beam is translated and also under the control of the digital computer 21.

Turning next to a more detailed consideration of the optical devices 14 and 15, the function of the first optical device 14 is to redirect or bend" the laser beam from its initial direction along the X axis to a quadrature direction along the Y axis. This is accomplished preferably by means of a known optical device called the pentaprism which is operative to receive the initial portion 11a of the laser beam in its collimated (focused at infinity) state and to reflect that beam so that the second portion llb of the laser beam which leaves the optical device 14 will be at 90 to the first portion lla, and still collimated. The pentaprism, although known to those skilled in the art, is described in greater detail and shown in the above-referenced application entitled LASER CUTTER OPTICAL SYSTEM of Robert M. Zoot and Douglas W. Wilson. In particular as disclosed in FIG. 3 of that application, the pentaprism is comprised of a pair of flat mirrors disposed at a 45 included angle between them. The incoming laser beam 11a is aimed at one of the mirrors from which it is reflected at the other mirror which it leaves at right angles to its incoming direction. In an actual system wherein the laser beam source 11 was a C laser model 41 manufactured by the Coherent Radiation Company of Palo Alto, California, generating a 250 watt beam with a diameter of one centimeter, the mirrors comprising the pentaprism were each a 1 /2 inch diameter silicon substrate coated with a dielectric coating selected to be an efficient reflector at 10.6 micron wavelength.

It will be understood of course that the pentaprism represents only one type of optical arrangement for changing the direction of the laser beam by 90, several others being also disclosed for sake of example in the Zoot/Wilson application.

Several alternative arrangements may also be utilized for the second optical device 15. Two of these are illustrated in FIGS. 2 and 3. In FIG. 2 the optical assembly is seen to comprise a horizontally oriented focusing lens 45 and a flat mirror 47, inclined 45 to the vertical, both housed in a casing 49 having an inlet window 51 and an outlet window 53. The collimated, redirected laser beam llb emerging horizontally from the first optical element 14 and entering the second optical device 15 through its inlet window 51, is focused by the focusing device 45 and is changed from its horizontal direction to a final vertical direction aimed at the conveyor work support surface 17 by the inclined mirror 47 through the housing outlet opening 53.

The alternative optical device 15a in FIG. 3, disclosed in detail in the aforementioned Zoot/Wilson application, is comprised of a housing 55 containing a focusing mirror 57 at one of its ends which receives the collimated laser beam 11b through an inlet opening 59. From the mirror 57 the laser beam is reflected onto a flat mirror 58 which is inclined 45 to the floor of the housing so as to reflect the beam out of the housing 55 through an outlet opening 61. The focal length of the mirror 57 is selected as as to bring the beam reflected therefrom to a focus at the conveyor work support surface 17 or slightly above it, depending upon the thickness of the material which is to be cut. In the abovementioned system which has been built, both of the mirrors 57 and 58 had a one inch diameter and were silicon substrates coated for high reflectivity at 10.6 micron wavelength, with the focusing mirror 57 having a radius of curvature of 12 inches. The distance between the mirrors 57 and 58 was selected to be approximately three inches, as was the distance from the mirror 58 to the work support surface 17, giving a focused spot diameter of approximately one thirty-second of an inch where the beam was intercepted by the material lying upon that work support surface.

Yet another possible alternative for the focusing system for the laser beam is disclosed in the abovereferenced application Ser. No. 3,627 by Howard R. Friedrich for a LASER LENS COOLING SYSTEM. In that system the positions of the elements 45 and 47 shown in FIG. 2 of the present application are reversed so that the collimated laser beam 11b first strikes a mirror so as to change the beams direction to the vertical, and the vertically downwardly projected final portion of the laser beam is then focused by a focusing lens system having a vertical axis from which it emerges toward and impinges upon the work support surface 17.

One of the important advantages of the system disclosed herein is that it permits the cutting of fabric in a single layer. FIG. 4 illustrates how a single layer of fabric may be held upon the work support surface 17 while the by-products of the laser cutting operation are being removed and the ignition of the cut fabric is being inhibited. In accordance with this aspect of the invention the work support surface 17 presented by the conveyor is air-permeable and air is drawn away from the underside of that surface by means of a chamber 63 which extends under the surface. Air is exhausted from the chamber 63 through an exhaust duct 65 by a conventional exhaust fan (not shown), causing the air pressure under the support surface 17 to be lower than that above it, and air and smoke to be drawn down through the support surface 17 and away from the system. It should be noted that this method of smoke removal and holding down of the material lying on the support surface has certain drawbacks, the principal of which is thatsome of the by-products of the cutting operation, such as smoke, tend to become lodged in the cut material. Therefore, alternative means may be employed for holding the cloth upon the air-permeable support surface 17 and for removing most of the cutting byproducts generated. One of these is disclosed in the above-referenced application Ser. No. 184,139 filed by Castro et al., entitled MATERIAL HOLDING AND SMOKE REMOVAL SYSTEM FOR A LASER CUT- TER. In the system disclosed in the referenced application, rather than to draw air directly down through the air-permeable support surface 17, it is caused to flow along and across that surface above it, after which it is redirected so as to flow back across that surface underneath it. In this manner by-products of the cutting operation, such as smoke, are removed without trying to pull them through the cut material which, moreover is held against the support surface 17 by the pressure differential which exists between the air which flows above the surface and that which flows below it.

Returning to the exemplary environmental control illustrated in FIG. 4, ignition of the fabric which is being cut is controlled by directing a flow of gas through a small pipe 67 at the cutting area 69. The gas may be an inert gas such as nitrogen, in order to extinguish any flames which might be produced. Alternatively it has been found that if air is blown through the pipe 67 at the ignition area 69 at a sufficient velocity, it will extinguish any incipient flames through the same action by which a candle is blown out. To aid in the removal of debris created at the cutting area 69, an additional exhaust pipe 71 may be provided whose inlet is positioned next to the cutting area and from which air is exhausted by conventional means so as to evacuate most of the undesirable debris.

The gas which is to be discharged through the pipe 67 is supplied through an inlet pipe 73 which also serves to pressurize the inside of the housing 66 in which the optical elements are contained and from which the pipe 67 extends. By thus pressurizing the housing, a continuous airflow can be maintained through the inlet and outlet openings of the housing through which the laser beam enters and exits, thereby preventing the entry of undesirable debris therethrough. Alternatively, as shown in the referenced Castro et al. application on ENVIRONMENTAL CON- TROL AT LASER CUTTING POINT, air may be caused to flow across the outlet window, through which most of the debris would tend to enter the housing, so as to create an air curtain to prevent contamination of the optics within the housing. It will be understood of course that, whereas the chamber 63 under the movable support surface 17 is stationary, the portions of the environmental control system which are located above the support surface are movable with the optical assembly contained in the housing 66, this applying particularly to the pipes 67, 71 and 73.

DETAILED DESCRIPTION OF THE EXEMPLARY SYSTEM the signals controlling the cutting and printing elements emanate, and a control booth 79 in which the operator is seated and which contains the computing elements of the system. 2. The cutting and printing unit a. In general I Turning first to a detailed description of the cutting and printing unit 75, it is comprised principally of the conveyor 17, the fabric spreader 43 at one end of the conveyor, a scrap disposal unit 85 shown in dashed line at the opposite end of the conveyor, and two cutting areas 13A and 13B alternating with two printing areas 91A and 91B disposed along the length of the conveyor 17 between the spreader and the scrap disposal units 43 and 85.

b. The conveyor 1 The conveyor 17 performs several tasks in the cutting and printing system. When its belt is in motion, it transports fabric from the spreader 43 at one end to a cut piece pickup area 90 near the opposite end. Additionally, the stationary framework portion of the conveyor 17, including principally a pair of steel beams 95 held by a set of legs 97, provides rigid support for the lasers 11A and 11B a pair of cutting and printing crossarms, the spreader assembly 43 and the scrap disposal unit 85.

In a particular unit proposed for construction, the conveyor assembly including the above-mentioned equipment would be approximately 87 feet long, 9 feet wide and 4- /2 feet high. The conveyor would provide a level work surface area approximately feet long by 5 /2 feet wide located approximately 3 feet above the floor. It will be understood of course that the above figures are mentioned merely to illustrate the magnitude of the apparatus shown in FIG. 5 rather than to imply that those figures are inherently necessary.

The conveyor '17 illustrated in FIG. 5 is divided into seven functional zones in the following manner. The spreading function, whereby material is spread onto the support surface formed by the conveyor belt is performed in the first approximately l2 foot long portion of the conveyor. A permanently mounted fabric spreader 43 ofa type normally used in apparel cutting rooms occupies the initial 2.5 feet and the remaining 10 feet are left unobstructed to help in the visual inspection of the unrolled fabric for flaws or creases. The cutting and printing zones 13A, 1313, 91A and 918 would each be 10 feet long in the proposed machine and, for reasons which will be explained hereinafter, would be separated by a 5 foot buffer zone 98. The last five zones 91A, 13A, 98, 91B, and 13B, which in the proposed machine would comprise a 45 foot long section of the conveyor 17, are dimensionally critical because of the limited focal length of the optics used to focus the laser beam upon the material which is supported by the conveyor. Particular attention should therefore be given to assign fabrication tolerances which will assure the necessary flatness over the entire 45 foot long area to maintain the material held by the conveyor 17 within the focused portion of the laser beam.

The sixth functional zone of the conveyor 17 is a pick-up zone 90 which in the proposed machine would be approximately 21 ft. long and which is left unobstructed to permit access for either manual or automatic piece part pick-up. Part of this pick-up zone is cut away in FIG. 5 to reduce the size of the drawing. Finally, the remaining few inches of level surface between the plck-up zone 90 and the end of the conveyor 17 falls within the operating zone of the scrap disposal apparatus indicated at 85. Not shown in FIG. 5 is the chamber 63 of FIG. 4 which encloses the underside of the conveyor 17 at least in the cutting areas 13A, 1138.

Turning next to some of the details of the conveyor 17, it is Comprised principally of a plurality of long and slender slats 99, one of which is illustrated in part in FIG. 6. The use of such slats featuring an aluminum open-celled honeycomb panel M11 is not applicants invention. Instead the concept of the open-celled honeycomb panel itself as a suitable support surface to with stand a focused laser beam is the invention of Robert M. Zoot by whom the above-referenced application Ser. No. 3,665 was filed thereon. As explained in that application, a honeycomb panel, preferably of aluminum with a wall thickness of the order of 0.004, is capable of supporting a layer of material being cut by a focused laser beam. Due to the scattering of the focused beam by the knife-like edges of the honeycombs open cells the panel is not damaged thereby. Nor does it reflect the laser beam upward where it might damage the material or the equipment. Instead the laser beam panes through the honeycomb cells and, once through and defocused, may be absorbed by a heat absorbing panel, such as aluminum. Furthermore, the concept of configuring a conveyor out of a plurality of slender slats made of the Zoot-type honeycomb is the invention of Georgette S. Egan, applicant in the above referenced application.

As shown in FIG. 6, the honeycomb slat may be constructed by providing a strip of honeycomb material 101 supported upon a casting 103, preferably aluminum, held rigid by tensioning rods 105. The slats are interconnected into a conveyor belt by means of chains (not shown) attached to their corresponding ends 109. Alternatively, the honeycomb slats may be made lighter by dispensing with the aluminum casting 103 and the tensioning rods 105 and by bonding instead a pair of thin support members to the opposite longitudinal edges of the honeycomb panel 101, with the top edges of the support members being beveled to a knife edge to prevent undesirable reflections from them. Such a honeycomb slat is disclosed and claimed in the abovereferenced Egan application.

Subject to control signals from the control booth 79, the conveyor slats 99 are moved by their connecting chains as a single conveyor belt by a drive motor (not shown) through conventional coupling gears and sprockets. To help the conveyor slats 99 to move smoothly along the steel beams 95, they are provided at their four corners with plastic (typically DELRIN) pads 110 which slide along the suitably finished top surfaces of the beams. Preferably the support beams 95 will have precisely machined surfaces covered by a lubricant to minimize friction and wear while also insuring that the slats which ride on them will form a precisely level work support surface. In this connection it is important to give attention to maintaining the sag of the individual slats 99 within acceptable limits dictated by the depth of focus of the laser beam.

c. The spreader Cloth to be supported and transported by the conveyor 17 is dispensed from the fabric spreader 43 which is anchored at the upstream end of the conveyor and on which a bolt of fabric 111 is rotatably supported on a frame 113. It will be noted that the spreader 43 is shown to have a set of wheels at the bottom of its frame 113. This is so because the spreader which has been proposed for use in the exemplary system of FIG. is one of conventional construction whose manner of operation is that the entire spreader is moved along its wheels along a level surface onto which the material resting upon the spreader is unrolled as the spreader is moving along. The functions of the fabric spreader 43 and of the material holding surface 17 in the exemplary system of FIG. 5 are reversed, with the fabric spreader remaining stationary and the work support surface moving, thereby drawing the fabric away from the spreader. This concept of reversing the functions of spreader and work support surface is also the invention of Georgette S. Egan and is separately claimed iln her above-referenced application.

As disclosed more fully in the Egan application, a CRA Champion model spreader is modified by coupling a gear with which that model senses the rate of spreader travel along the material support surface to the sprocket shaft of the conveyor 17. The sensing gear drives a shaft on the spreader, and control devices on the latter turn the bolt 1 11 at a rate which will dispense cloth therefrom at a proportional linear rate. By proper gear ratio selection, the bolt 111 upon the stationary spreader 43 is caused to feed cloth onto the conveyor belt at the same linear rate at which that belt travels.

Alternatively, as disclosed in the above-referenced Castro, Toscano, Newton application on TENSION- FREE CLOTH DISPENSING APPARATUS, the spreader may be controlled by introducing a freehanging loop into the material between the spreader 43 and the conveyor belt. The length of the loop is sensed by photocells so that bolt 111 is turned in response to the loop becoming shorter than a predetermined minimum.

THE CROSSARM ASSEMBLY Returning now to the cutting and printing unit 75, as mentioned earlier it includes a pair of cutting areas 13A and 13B alternating with a pair of printing areas 91A and 91B. Referring both to FIGS. 5 and 7, the first area through which cloth from the bolt lll moves is the printing area 91A within which a printer crossarm assembly 127 operates to move a printing element mounted upon a carriage 169 anywhere within the printing area. A similar cutter crossarm assembly 127 moves within the first cutting area 13A just next to the printing area 91A. Since all of the crossarm assemblies are essentially identical whether they carry a cutting head or a printing head, they will all be identified by the reference numeral 127. Moreover, for sake of brevity, in the following discussion of a cutter crossarm assembly 127 shown in FIG. 7 it will be referred to by the abbreviated name crossarm assembly.

The function of the FIG. 7 crossarm assembly 127 is to transport a pair of optical elements, such as the elements l4 and 15 of FIG. 1, within the cutting area 13 along the X direction so that the first optical element 14 remains in the path of the collimated laser beams first path portion 11a. In addition the crossarm assembly 127 also serves to transport the second optical element 15 relative to the first, along the Y axis so that the element 15 remains in the path of the collimated laser beams second path portion 11b. This is accomplished in the exemplary system of FIG. 5 by aiming the laser beam precisely parallel to the longitudinal (X) axis of the conveyor 17 and moving the first optical element 14 precisely in line with the laser beam so aimed. The first optical element 14 is then made operative to redirect the laser beam exactly from its initial direction so that it becomes projected in the Y direction across the width of the conveyor 17 and across the width of the cutting area 13.

Spanning the width of the conveyor 17, the crossarm assembly 127 has a relatively broad base 128 at one end which rides along a supporting rail 129 mounted upon the steel beam 95. Extending from the crossarm base 128 is a crossarm 131 held rigid by a pair of braces 133 and supported at its opposite end upon a second supporting rail 135 mounted upon the beam on that side, the tip of the corssarm 131 being supported upon the rail by means of a sliding bracket 137.

The crossarm assembly 127 is driven along the X axis by means of an electric motor 139 through a belt 141 which is coupled to and rotates a lead screw 143 extending along the top of the guide rail 129. Also extending along the supporting rail 129 next to the lead screw 143 is a way 145 upon which the crossarm base 128 is guided by a pair of bushings 146 rigidly attached to the base 128 and riding on the way (cylindrical guide rail) 145. The first optical assembly 14 (FIG. 1) is mounted near the crossarm base 128 so as to move therewith along the X axis in the path of the first portion of the laser beam. An appropriate mounting place is indicated in FIG. 7 by the block 148, with the first optical assembly 14 being omittedfor sake of clarity. The second optical assembly 15 (FIG. 1) is mounted on a second block 150 which is actually a carriage movable toward or away from the first mounting block 148 so as to maintain the optical assembly 15 (not shown in FIG. 7 for sake of clarity) in the path of the laser beam emanating from the first optical assembly 14 carried by the first block 148.

The carriage 150 is transported along the crossarm 131 by means of a Y axis electric motor 149 through a belt 151 and through a lead screw 153 which extends the length of the crossarm 131. A Y axis way 155 is also provided next to the lead screw 153 to help guide the carriage 150. The position of the carriage 150 along the crossarm 131 is monitored by means of a resolver 157 mounted at the tip of the crossarm 131 and geared to the lead screw 153. A similar resolver (not shown) may be geared to the X axis lead screw 143 to monitor the crossarm position along that axis.

To implement the concept of smoke removal illustrated schematically in FIG. 4 an air scoop 159 is provided inside the carriage 150 and is connected by means of a coupling 161 to an air duct 163 which runs along and above the crossarm 131 and whose top face is air-permeable to permit communication with the coupling 161. The duct 163 is connected at one of its ends through a further coupling 167 to a second duct which runs along the X axis supporting rail 129 crossarm the corssarm base 128. Air is exhausted from one end of the second air duct 165. Both of the couplings I61 and 167 are slidable along the tops of their respective ducts 163 and 165 so that a continuous airflow is maintained through the system away from the scoop 159 inside the carriage 150.

The printer crossarm assembly 127 for transporting a printing unit within the printing area 93 is identical to the crossarm assembly 127 illustrated in FIG. 7, except that the smoke removal components are omitted and of course it carries no optical elements. Instead it carries a non-contact printing device of conventional construction upon its transport carriage 169. Also to take best advantage of the available space, the base portion of the printer crossarm assembly 127 is on the opposite side of the conveyor 17 from the base portion of the crossarm assembly 127. A suitable non-contact printer to be carried by the carriage 169 is marketed by the A. B. Dick Company under the name of VIDEO JET. The VIDEO JET operates like a miniature fluid nozzle, dispensing a uniform ink stream from a nozzle tip. The nozzle is modulated electro-mechanically at a high frequency to break the ink stream into uniform droplets and the ink stream is modulated electrically to deflect the particulated ink stream as a function of an electric charge imparted to it. For the exemplary system of FIG. 5 the nozzle assembly would be used without modulating either the ink stream or the nozzle. Instead a continuous stream would be dispensed, with printing being accomplished by moving the carriage 169 along the X and Y axes to permit character generation as well as the drawing of any type of guide line. When a no-print condition exists, which is usually most of the time, the ink stream would be deflected into a gutter (not shown) from which it would be returned to the ink reservoir, thereby reducing ink consumption to about one-sixtieth of a quart per hour for the VIDEO JET printer. Filtering of the circulated ink in the high lint environment which is to be expected will be a critical requirement to which careful attention will have to be paid.

The crossarm method of traversing the cutting and printing units is only one of many possible alternatives. In another system built for the assignee of the present invention, a different mechanism was employed which may be preferable in some applications where high speed and low inertia are controlling considerations. This mechanism was manufactured by Xynetics Inc. of Canoga Park, California and is described in Sawyer US. Pat. No. 3,376,578. Briefly, a platen containing a grid of magnetic material is mounted over each cutting or printing area. In the cutting areas 13A and 13B a pair of linear motors are carried on the underside of each platen upon which they are stepped digitally in the X and Y directions. To perform the function of a crossarm 127 the two motors are moved on common Y coordinates along the X axis. The first of them travels along the outer edge of the cutting area 13 and carries the first optical element 14. The second linear motor carries the second optical element 15 and moves not only along the X axis with the first motor, but also moves relative to it along the X axis, just as the crossarm carriage 147 travels relative to the mounting block 148. In the cutting areas 91 only the second linear motor is required, carrying the printing unit along the X and Y axes.

A cloth panel cut by means of the exemplary system of FIG. 5 is illustrated in FIG. 8. The panel is seen to be cut in accordance with a pattern in a series of straight line segments 170, the starting and stopping points 172 of which are denoted by small circles. The number of line segments 170 and their length are selected so that the maximum deviation of the cut piece from the actual pattern will be less than, or equal to, a specified tolerance. In the proposed system this tolerance was specified as 0.0625 inches.

FIG. 9 serves to explain a source of error which tends to occur in executing a pattern such as that shown in FIG. 8, this error being inherent in a type of servomechanism which may be used to advance the second optical element 15, hereinafter referred to as the cutting head, in the X and Y directions with the crossarm assembly 127. If the servomechanism used is of a type having an appreciable velocity following error, the element which is being moved by the servomechanisms in the X and Y directions will lag in actual position the position where it is commanded to be at any given instant by the signals being fed to the servomechanisms. As shown in FIG. 9 for example, the first path segment extends from a starting point 171 to a terminal point 1'73 from which the second segment extends toward the right to a point 175. Because of the following error, the commanded element such as the cutting head 15 will fall short of its commanded position 173 at time T1 and will only be at point 177. Consequently, to permit the commanded component to move toward its desired position 173, a dwell time AT is provided before the next motion command is applied to the servomechanism. Moreover, because there is a permissible error E which represents the distance by which the commanded element may miss its commanded point 173, the dwell time AT need not be made long enough to permit the element to move all the way to its commanded point 173 but may instead be terminated before that time, and the next command may be applied to it at time T2, which in the illustrated example is a purely X command, causing the commanded element to veer toward its second target point 175 such that it misses the first commanded target point 173 by a distance E. Stating it differently, in the exemplary system illustrated in FIG. 5 the acceleration and deceleration at the ends of the programmed line segments are also programmed. This acceleration/deceleration function is implemented by including a dwell time command as part of each control tape data block, wherein each block represents a series of movements to be executed by the crossarms 127 during an operating period. The dwell time or time delay at the end of each line segment 170 will be computed by the Crossarm computer 21 as a function of four variables: Line segment length, initial velocity of the cutting head at the start of the line segment, allowable cutting tolerance E, and turning angle of the cutting head from a given line segment to the next.

To execute the movement illustrated in FIG. 9 the cutting head would be programmed for a combined X axis and Y axis displacement, taking it from the point 171 to the point 173 through axis components X1 and Y1, representing one straight line segment 170. This would be followed by a dwell time for that same line segment 170, starting at T1 and ending at T2. The dwell time command would be followed by a programmed X axis displacement, representing movement to execute the next straight line segment 170 from the point 173 to the point 175 through a distance X2. As will be explained hereinafter, although the commands as received from the production tape (FIG. 1) are incremental displacements, these commands are converted in the digital computer 21 and the positioning electronics 19 of the system into synchronized X and Y axis servo velocity commands, typically a series of pulses. For example, the commanded displacement X1 would be converted to a constant velocity for a time T1. At time T1 the X axis velocity command goes to zero but because of the velocity following error, the X axis position at this time is only XTl. The conclusion of the velocity command at time T1 coincides with the beginning of the dwell time AT. During this time the movement along the X axis decelerates and the position at the end of the dwell time AT is XT2. However, since neither the X axis position nor the Y axis position is required to go to the ideal end point 173, the next position command X2 may be issued at this time T2. Thus the velocity command corresponding to the next incremental distance X2, representing the distance along the X axis between the points 173 and 175 may be issued to be executed during the time period which begins at T2 and ends at T3. The length of the dwell time AT is computed so that the total error E will be less than or equal to the maximum permissible error, assumed previously as 0.0625.

It should be understood that the only reason for delving into this aspect of servomechanism design is because in the following detailed description of a suitable electronic circuit for driving the servomechanisms, provision is made to insert a dwell time at the end of each path segment, so as to minimize the following error inherent in the servomechanisms that are described herein. However, there are other types of servomechanisms such as that described in the abovereferenced Sawyer patent, which do not have the velocity following error that necessitates the provision of a programmed dwell time and to which the explanation given with reference to FIG. 9 would be irrelevant.

3. Crossarm Allocation of Marker Segments a. In general Summarizing what has been described thus far, the exemplary cutting and printing system of FIG. 5 features a pair of cutting areas 13A and 138, each of which contains a separate cutting device, a pair of cutting areas 91A and 918 containing respective printing devices. The use of two separate cutters sharing a common computer 21 represents a preferred embodiment of the invention. What will be described next is a particularly advantageous organization of the elements of the system of FIG. 5 whereby in accordance with the present invention the cutting workload may be divided between the cutting heads 15 in the cutting areas 13A and 133 in a straight forward manner. Yet, by virtue of the system organization which will be described, the cutters between them will cut every required part without getting in each others way. Because the respective tools in the exemplary system of FIG. 5 are laser cutting heads carried by respective crossarms 127, the workload allocation concept of the present invention will be referred to hereinafter as Crossarm allocation.

b. Detailed discussion of producing a cutting sequence tape Before explaining Crossarm allocation in detail, it will be helpful to summarize the manner in which one would generate and store the data representing the patterns according to which garment parts are to be cut by the system from a layer of fabric. A portion of a length of fabric from which parts are to be cut for a garment is shown in FIG. 11. Typically, fabric is divided into lengths of the order of 30 feet and the parts for up to three mens suits are cut'from that length of fabric. Generally, the patterns corresponding to the various parts which are to be cut are laid out by people who are skilled in so arranging the patterns as to leave a minimum of space between them, thus minimizing fabric wastage. It is a portion of such a layout that is shown in FIG. 11 which contains most of the parts for a mans suit. Thus the trouser parts are discernible along the top of the material 179 in FIG. 11, and the panels 181 for a mans jacket are seen at the lower right-hand corner thereof.

The portion illustrated in FIG. 11 represents approximately one third of a 30 foot length of fabric, the collection of patterns representing the parts to be cut from that length of fabric being commonly referred to as a marker. In the exemplary system the electrical signals digitally representing the patterns according to which parts are to be cut are stored on a roll of magnetic tape, referred to herein as the cutting sequence tape 25. The cutting sequence tape is compiled through a series of steps which involves generally (I) the designing of a garment, (2) the conversion of each part of that garment into digital signals representing the pattern for those parts by means of a digitizer, (3) the production of a pattern tape containing digital signals representing the digitized patterns, (4) the production of a marker tape containing the relative positions of the patterns making up the garment (and perhaps those making up an additional garment as well) and (5) the combination of the contents of the marker tape and the pattern tape into the final cutting sequence tape 25.

Referring to FIG. 12, the first of the above steps is performed by an artist who designs a new garment and produces a drawing thereof. From that drawing a set of heart-size (Size 42 for mens clothes) patterns are produced. The heart-size patterns 183 are then placed one at a time on a digitizer table 185 which is a commercially available device having a large flat surface upon which the pattern is placed and a follower device is provided which can trace along the perimeter of the pattern. By means of transducers and electronic circuits the digitizer converts the successive physical positions of its follower into digital signals representing the X and Y coordinates of the successive positions of the follower and therefore of the perimeter of the pattern.

The digitized heart-size pattern data, encoded as described above and recorded on magnetic tape, is fed into a digital computer containing the grading formula in permanent memory. lnstructions are produced by this computer to prepare patterns for all commercial garment sizes by means of digital plotter. The plotted patterns for each size are cut out and are then used by a marker expert to prepare manually the individual markers on the basis of efficient textile material utilization. The pattern location for each marker prepared on the digitizer table is encoded by this instrument. The marker tape preparation sequence for a given style is complete when all commercial garment sizes for that style are encoded on magnetic tape by the digitizer as described above.

The digitizer is used in the marker encoding process above to provide three types of data. These include: (1) a description of the particular part; (2) a location key; and (3) an alternate origin point. The meaning of the location key and of the alternate origin point will be better understood by referring again to FIG. 11, and to the trouser part 180 illustrated therein. For each pattern the location key consists of three points 187, 189 and 191. The first point 187 is located at the lower lefthand corner of the part, called the origin. The second point 189 is located at the right end of the part at the same Y coordinate as the point 187 but at a different X coordinate. The third point 191 of the location key is directly above the second point 189, at the same X coordinate but at a different Y coordinate. By defining the location of the key of a given pattern, that is by defining the location of its three points 187, 189 and 191, the location and orientation of the entire pattern is unambiguously defined. Thus, each of the parts as shown in F 1G. 11 has a key whose desired location relative to every other part on the fabric 179 is stored in a manner to be explained.

Diagonally opposite from the first (origin) key point 187 is the alternate origin 1930f the part and of its corresponding pattern. By providing an alternate origin for the part it is possible to begin cutting it from that point rather than from the origin point 187 which may yield a shorter path length between that pattern and the next pattern to be cut, this path length being referred to as a dry haul.

The description of each pattern is produced by means of a typewriter keyboard associated with the digitizer, by means of which numbers or letters, or a combination of both, may be entered into the storage medium upon which the position information is stored by the digitizer, these characters serving to identify the particular pattern which has been digitized.

The pattern tape 19S produced as described above which contains the digitized patterns for all commercial size garments is arranged so that any pattern for any size can be read from the tape by referring to the part number of that pattern. Additionally it is required that the data on the tape be in a language'or form compatible with a digital plotter so as to permit the patterns on the tape to be plotted as described above for marker preparation and checking purposes.

More specifically, )4 scale patterns 199 are used in the marker preparation process. These /t size patterns are then laid out on a sheet of paper into the most compact configuration by a marker expert such as that shown in FIG. 11. This step is done manually at the present time, but may later be automated using computer software. The resulting size marker 211 is then placed on a digitizer 213 which may be of the same type as the digitizer referred to earlier, and by means of the digitizer 213 several types of data are derived from the marker 211. These include: (a) identification of the pattern part; (b) identification of the marker containing the pattern; and (0) location of the pattern key. The data generated by the digitizer is then edited by means of the same computer used to edit the pattern data. This serves both to convert the digitizergenerated data into plotter-compatible language and to uncover errors introduced during the digitizing process. The resulting edited data is stored on a magnetic tape labelled Edited Markers 215 in FIG. 12, which contains the precise locations of all patterns comprising the whole marker as well as the identification legend for each part of the marker. At this point the edited marker and pattern tapes 215 and are placed into a marker library 217 and a pattern library 219 respectively. Also at this time a marker catalog 221 is printed from the marker tape 215 which includes identification of the marker, its number, its maximum X and Y dimensions and its size. A pattern catalog 223 is also printed, it containing the number of each pattern and the number of the model of which it is a part.

Using the marker catalog 221, the pattern catalog 223, information concerning plant capacity 225, customer orders 227 for particular garments, and piece goods in stock 229, a production schedule determination 224 is made. The production schedule determination 224 is recorded on a work order sheet on which the scheduler notes both the number of the markers which contain the desired patterns and the material from which the parts for the ordered garments are to be cut. Preferably customer orders for garments will be arranged so that each customers order will be completed before the next customer's order is cut.

To facilitate processing of the work order sheet, it is key-punched onto cards acceptable by a general purpose computer such as the lBM 360/30. The keypunched work order is then applied as the input to such a general purpose computer which is next used to compile the cutting sequence tape 25 therefrom. The process whereby the contents of the work order sheets are transformed into the cutting sequence tape 25 will typically include more than one processing run by the computer. During the initial run a production schedule sequence tape 231 is generated, this tape containing in proper order the identities of all markers required to fill the orders on the work sheets. As part of this run the 

1. A method of guiding a plurality of tools along the perimeters of a set of patterns distributed along an elongate surface movable along its longitudinal axis in response to signals representing the perimeters and locations of said set of patterns in their desired positions on said surface, comprising: a. assigning to each said tool an area of operation which extends along said axis by a length which is at least twice the longest dimension of any of said patterns along said axis and spacing apart said areas along said axis; b. successively advancing said elongate surface along said axis through said areas of operation in equal steps so that after each said step a successive one of a first series of spaced apart groups of said set of patterns is positioned fully in one of said areas of operation, said areas of operation being spaced from one another so that after each said step a successive one of a respective additional series of spaced apart groups of said set of patterns, whose member groups alternate cyclically with member groups of said first series of spaced apart groups, is positioned fully in each of the other of said areas of operation; and c. after each said advancement actuating each said tool with the signals representing the patterns in the pattern group then located in the area of operation of that tool.
 2. The method of claim 1 characterized further in that said tools are actuated by: a. assigning to each said tool a respective series of spaced apart, transverse segments of said surface, with members of the respective series cyclically alternating, all of said segments having the same width which is no greater than half the length of the area of operation of the tool to which said segments are assigned; b. so spacing the tools along said axis that after each advancement of said surface a successive segment of a respective series of said segments is centered in each of said areas; and c. after each advancement applying to each said tool the signals representing all patterns whose longitudinal midpoints along said axis fall within the segment centered in the work area of that tool.
 2. to successively position fully within the work area of the other of said tools a second series of alternate segments of said material which are to be operated upon along the perimeters of a second series of said set of patterns, members of said first and second series of segments alternating with one another; and d. control means for operating each of said tools in response to those signals which represent the patterns along whose perimeters material segments in position in the work area of that tool are to be operated upon.
 2. traversing said beam over said operating area along the perimeters of those of said patterns whose reference points fall within the transverse strip stopped within said area; and
 2. traversing said beam over the operating area assigned to said given tool along the perimeters of those of said patterns whose longitudinal centers fall within the transverse strip stopped within said area; and
 3. turning off said projector when said beam is between said patterns.
 3. turning off said projector when said beam is between said patterns.
 3. The method of claim 2 characterized further in that said signals digitally represent successive segments of successive pattern perimeters and are applied to each said tool serially, segment after segment, pattern after pattern until said tool has been guided along the perimeters of all patterns positioned fully within its work area.
 4. A method of guiding a pair of tools along the perimeters of a set of patterns positioned over an elongate surface movable along its longitudinal axis in response to a record of signals representing the perimeters and locations of said patterns comprising the steps of: a. assigning to each said tool an area of operation which extends along the longitudinal axis of said elongate surface by a length L which is at least twice as long as the longest dimension of any of said patterns along said axis, and spacing apart said areas along said axis by an odd multiple of L/2; b. advancing said elongate surface along its longitudinal axis through said assigned areas of operation in a series of steps, each L long and stopping said surface after each advance so that a successive transverse strip of L/2 length is located fully within the first of said assigned areas; c. actuating one of said tools when the first and subsequent odd transverse strips are located in its Assigned area of operation, said actuation being in response to the signals representing those patterns whose longitudinal centers along said axis fall within said first and subsequent odd transverse strips; and d. actuating the other one of said tools when the second and subsequent even strips are located in its assigned area of operation, said actuation being in response to the signals representing those patterns whose longitudinal centers along said axis fall within said second and subsequent odd transverse strips.
 5. A method of claim 4 characterized further in that: a. said tools include laser beam projectors; b. said elongate surface carries a layer of material through which said patterns are to be cut by said beams; and c. actuation of a given one of said tools includes:
 6. A method of guiding a tool along the perimeters of a set of patterns over an elongate surface movable along its longitudinal axis in response to a record of signals digitally representing the perimeters and locations of said patterns comprising the steps of: a. assigning to said tool an area of operation which extends along the longitudinal axis of said elongate surface by a length L which is at least twice as long as the longest dimension of any of said patterns; b. advancing said elongate surface along its longitudinal axis through said assigned area of operation in a series steps each L/2 long and stopping said surface after each advance so that a successive transverse strip L/2 in length is located fully within said assigned area; and c. actuating said tool, after each successive transverse strip has stopped fully within its assigned area of operation, in response to the signals representing those patterns whose location along said axis bears a predetermined relationship to said stopped transverse strip.
 7. The method of claim 6 characterized further in that: a. said tool includes a laser beam projector; b. said elongate surface carries a layer of material through which said patterns are to be cut by said beam; and c. actuation of said tool includes:
 8. The method of claim 7 characterized further in that said predetermined relationship is that the longitudinal center of said pattern along said axis falls within said stopped transverse strip.
 9. A method of guiding a tool, which is movable within a flat plane, along the perimeters of a set of patterns over an elongate panel of material in response to stored signals digitally representing the perimeters and locations of said patterns on said elongate panel, comprising the steps of: a. providing said tool with an operating range which extends along said selected axis farther than twice the longest dimension of any of said patterns; b. advancing said panel of material in a flat condition along said axis and substantially parallel to said plane in successive equal steps, each step bringing a successive transverse reference strip of equal width of said panel of material into the operating range of said tool; and c. traversing said tool over each transverse reference strip that has come within its operating range in response to the signals representing those patterns whose location along said axis bears a predetermined relationship to the position of said transverse reference strip along said axis.
 10. The method of claim 9 characterized further in that said relationship is that the longitudinal center of said pattern falls within said reference strip.
 11. Apparatus comprising: a. a record medium containing signals representing the perimeters and locations of a set of patterns to be cut through an elongate panel of material; b. first and second tools, each having means for traversing it independently of the other over separate work areas, each work area being at least twice as long as the longest of said patterns; c. means for moving said panel of material along its length successively through said work areas in equal steps whose length relative to that of said work areas is selected
 12. A numerically controlled tool responsive to a record medium containing signals representing the perimeters and locations of a set of patterns to be followed along an elongate panel of material and comprising in combination: a. means for providing signals representing the perimeters and locations of a set of patterns to be followed along an elongate panel of material; b. first and second tools each having means for traversing it independently of the other over separate work areas each work area being at least twice as long as the longest of said patterns; c. means for moving said panel of material along its length successively through said work areas flat, in equal steps whose length is selected to position respective sets of alternate, equally widthed, transverse strips of said material in said first and second areas respectively; and d. control means for operating each of said tools in response to those signals that represent the patterns whose location along said axis bears a predetermined relationship to the position of said transverse reference strip along said axis.
 13. The tool of claim 12 characterized further in that the width of each said reference strip along said axis exceeds the length of the longest of said patterns along said axis, and in that said predetermined relationship is that the longitudinal midpoint of said pattern falls within said reference strip.
 14. A system for guiding a plurality of cutting tools over an elongate panel of material so as to jointly cut a plurality of patterns through said panel in a desired array comprising in combination: a. a plurality of cutting tools spaced along a selected axis, each tool being movable in a plane within a separate work area; b. means for moving an elongate panel of material with its longitudinal axis aligned with said selected axis through a succession of stationary positions in said work areas so that a different set of spaced apart transverse strips of said panel becomes positioned in the work area of each of said cutting tools; c. digital servo means for moving each said tool within its work area independently of the other in response to a pair of velocity-representative pulse trains after each said movement of said panel; d. a cutting sequence tape having stored thereon a plurality of data groups, each data group representing the perimeters of those patterns whose longitudinal centers are to fall within a respective set of transverse strips successivEly positioned in a given one of said work areas, data groups representing patterns whose longitudinal centers along said axis are to fall in each said strip being separately identified with the tool in whose work area that strip is to be centered; and e. digital computing means for deriving from each said data group a pair of velocity-representative pulse trains and for applying said pulse trains to the respective digital servo means when the transverse strip which is to contain the longitudinal centers of the patterns represented by said data group is positioned within the work area of said tool. 